The invention relates to a preparation and crushing device, particularly for refuse materials, having a rotatably driven drum and at least one eccentricly disposed high-speed rotor, which rotates in the direction opposite to the direction of rotation of the drum.
The invention described below is described chiefly in connection with refuse materials, e.g. garbage, but can of course also be used for many other materials, examples of some being given below.
It is known that the increasing quantities of refuse produced by cities, parishes and industry, necessitate the manufacture of large refuse disposal plants. In this connection, the problem of preparation and crushing occurs at numerous stages of the process. This is also true with regard to the utilisation of raw material stocks in world trade and industry or of residue produced during manufacturing. Thus, a preparation and crushing device is sought which is able to process continuously or discontinuously and in large quantities materials of very varying compositions. The process is concerned primarily with crushing, mixing and sorting or sieving, these being activities which are required to be carried out either consecutively or simultaneously.
A crushing device, which has the features of the kind described at the outset, is already known for processing garbage and refuse material. The high speed rotor used therein is provided with at least one toothed, disc, the plane of which extends at right angles to the rotor shaft and partially submerges into the material held against the container wall by means of the over-critical rotational speed. This known crushing device may already be used in a wide range of applications, such as the processing of refuse even supplied in refuse sacks, of boxes and of materials in bundles. The known device functions according to the principle that the materials to be processed, particularly in the case of fine crushing, are held firmly against the interior wall of the container by virtue of the rotating container being driven at an over-critical speed and are crushed by means of a toothed circular disc. The critical rotational speed represents that number of revolutions per minute for the drive of the drum at which the centrifugal force is greater than the weight of the material being processed, so that the material is pressed against the interior wall of the drum.
However, the inhomogenity of the material, particularly with regard to refuse materials, presents difficulties under certain circumstances which lead to problems even in the case of the crushing device described above. It has, for example, been shown that an extremely uneven feeding results in high load peaks of the rotor drive so that the known device functions at times with an excessively high energy consumption. These load and energy peaks occur in particular in the case of correspondingly unsuitable material to be processed due to the fact that the distance between the rotor and the interior wall of the drum is purposely kept small therein.
The over-critical rotational speed of the known drum requires the inner surface of the drum to be smooth of course. It has been shown in the case of wet, slippery material that under certain circumstances this material slides past the interior wall of the drum and leads to blockages. The reason for this is the lack of friction between the drum wall and the material to be processed. On the other hand it is not possible to attach entrainment members to the interior wall because they would collide with wall strippers which are required to detach the layer of material from the drum walling and cause sifting and circulation.
Particularly coarse-grained material can lead to damage to the known crushing device due to the fact that lumps of metal enter the area between the rotor and the inner wall of the drum and cause damage on the zones of contact. For this reason it has been found necessary to incorporate a pre-crushing means and to provide a magnetic cut-out.
The problem of the invention is therefore, to provide a preparation and crushing device of the kind described at the outset, which, while avoiding load peaks and the need for additional machinery, permits material which may be voluminous, lumpy, coarse and hard to be processed, prepared, mixed and crushed using simple tools; if necessary, right up to the fine-fibred or flour-like dressing of the particles.